The present invention is concerned with the preparation of alpha-bromo-gamma-butyrolactone which can be used in the preparation of various useful chemicals such as the fungicides disclosed in Chan, U.S. Pat. No. 3,933,860.
H. Plieninger, Chemische Berichte, V. 83, No. 3, pp. 265-268 (1950) discusses the cleavage of gamma-lactones with alkyl mercaptides. Plieninger discloses preparation of 2,4-dibromobutyric acid bromide and its conversion into 2,4-dibromo-butyric acid, which in turn is converted into alpha-bromo-gamma-butyrolactone. In the Plieninger reaction sequence, 2 mols of bromine are added to 1 mol of butyrolactone in the presence of 0.4 mol phosphorus catalyst at a temperature of 25.degree. to 80.degree. C. to obtain the dibromobutyric acid bromide. Then this acid bromide is mixed with water to obtain the dibromobutyric acid. Finally, the dibromobutyric acid is refluxed with water to obtain alphabromo-butyrolactone.
Livak et al, JACS Vol. 67, p. 2218 (1945), "Synthesis of DL Methionine", discusses the reaction of 1 mol of gamma-butyrolactone with about 1 mol of bromine in the presence of 0.02 mol phosphorus tribromide at a temperature of 100.degree.-130.degree. C. and a reaction time of about 14 hours, followed by distillation under vacuum to obtain alpha-bromo-gamma-butyrolactone. Livak et al mention that the alpha-gamma-dibromobutyric acid obtained from the bromination can be converted to alpha-bromo-gamma-butyrolactone "on distillation or treatment with cold alkali".